FR2601616A1 - NEW PROCESS FOR OBTAINING SELF-ADHESIVE BLOCKS WITH NON-ADHESIVE SURFACE. - Google Patents

Abstract

BLOCKS OF SELF-ADHESIVE SUBSTANCES WITH NON-STICKED SURFACE ARE OBTAINED BY SELF-ADHESIVING MOLDS PREVIOUSLY COATED, BY SPRAYING, WITH A NON-SELF-ADHESIVE THERMAL FABRIC.

Description

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1.

  A method for packaging self-adhesive hot-melt adhesives is described, in the form of blocks with a surface devoid of any sticky or sticky character.

  The hot-melt self-adhesive compositions are industrially implemented using sizing machines which distribute the products in molten form, and the reservoirs of which are generally supplied from blocks or breads, most often in the form of cubes, more or less flat parallelipipeds, or pyramid trunks,

  whose volume varies from about 0.5 to 20 liters.

  The material of the hot-melt self-adhesive consists essentially of fusible resins, solid at room temperature, but whose surface remains permanently more or less sticky. This tackiness is the essential property of permanent adhesives, but the counterpart is, for breads or power packs, their agglomeration when they are brought into contact without protection, the attachment of all kinds of soiling, and great inconvenience , if not

  a certain insalubrity in handling.

  Certain hot-melt adhesives, such as, for example, long-setting hot-melt adhesives, without being strictly speaking

  stickers, can nevertheless-present the same phenomenon of self-adhesion with all its harmful consequences.

  The invention therefore relates to all adhesives capable of sticking to themselves by simple contact, under more or less high pressure, and in particular adhesives based on natural rubber, SBR rubber, SIS, SBS, SEBS, polychloroprene. , nitrile rubber, chlorinated rubber, butyl rubber, polysulfides, ethylenevinylacetate polymer and its copolymers, polyetheramides, polymers and copolymers of Go - olefins, adhesives based on natural or artificial sticky resins, rosin and rosin esters, petroleum resins and synthetic resins, plasticized or not,

  indene-coumarone resins, natural waxes, pitches or bitumens or modified with synthetic resins, polyesters, polyamides, polyacrylic etc ...

  All these products have, for a long time, been contained in blocks, breads or paving stones, individual elements or grouped in plates of individual elements, packed with non-stick sheets, generally made of paper or siliconized cardboard. Such packaging can also serve 40 advantageously as a mold during the shaping of the blocks by casting.

melted adhesive.

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  2. One thus finds in the trade, individual packaging in strong silicone paper for cubic blocks of 1 to several liters-, or boxes in cardboard boxes with multiple compartments (4 to 24) made of silicone paper, compartments whose capacities can vary from liter to several liters.

  These systems, although widespread, have a number of drawbacks.

  These lost packaging molds are expensive.

  Their material is poor conductor of heat and therefore, the cooling of the blocks is slow, the recovery and finishing of the blocks after their casting can only be done after a very long time, which contributes to the slowness of the rates and worsens

  the cost of the packaged products.

  The blocks, breads, pavers must be separated from their packaging at the time of their use, an operation which is all the less easy and all the more unpleasant the greater their surface adhesiveness.

  Attempts have been made to provide other solutions to this problem of packaging hot-melt pressure-sensitive adhesives and similar substances, for example by filming them by coextrusion with a substance making a non-sticky sheath, or by pouring the pressure-sensitive adhesive in a mold. metallic previously coated with powder and maintained by

  electrostatic (see French patent no. 83 03387).

  These processes, however interesting they may be, can be criticized with regard to the finish: non-protection of the cutting surfaces of the extruded shapes, non-protection of the upper surface of blocks cast in powdered molds. In addition, these techniques are ill-suited to the manufacture of self-adhesive units of various shapes and volumes.

  claimed by the machines that absorb them.

  The Applicant has produced a new method of manufacturing blocks, breads or pavers of self-adhesive substances, the surface of which is devoid of any sticky property, and having the following characteristics: the process is a process of pouring into a reusable mold;

  - The molded block consists, in its mass, of the self-adhesive or of the hot-melt substance which would have exhibited a certain surface adhesiveness, and on the surface, of an epidermis containing a non-self-adhesive hot-melt.

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  3. This epidermis is produced by lining the mold, coated with a permanent non-stick material, with a veil of hot-melt material; - The melted self-adhesive is then poured in a known manner, into the mold thus coated; - a veil of hot-melt adhesive is affixed to the free surface; - the block is removed from the mold as soon as the temperature is sufficiently low

  so that the part thus formed has reached the necessary consistency.

  In a preferred form of the invention, the protective veil is obtained by spraying, using a process known per se, with the hot-melt

  melted to obtain a veil quite similar in appearance and consistency to a nonwoven.

  This spraying is directed on the walls and the bottom of the cold mold, and continues until the mold is completely coated

with a thickness of 0.3 to 3 mm.

  The melted self-adhesive is poured by gravity into the mold thus lined.

  After sufficient cooling, the free surface is coated with a veil

  also applied by spraying the same hot melt product.

  Demoulding carried out after total cooling, delivers a block which does not adhere to any surface, or even to another block of the same nature. 20 Among the non-sticky hot-melt usable for the realization

  of the invention, there may be mentioned, without limitation: waxes, paraffins, waxy forms of antioxidants, non-self-adhesive hot melt adhesive formulas, polymers and hot melt copolymers of the ethylene-vinyl acetate type , polyethylenes, ethylene-maleic anhydride, ethylene acrylic acid copolymers, etc.

  The non-obviousness of the process and of the product obtained resides, not so much in the use of a hot-melt adhesive as an epidermis for non-stick isolation and as a release agent - which is at least already very unusual - but above all in the permanence of this protective veil, which retains its integrity and its function, while fusible from

    C / 80 C, it receives a liquid at 110 C / 180 C with which it is completely miscible in the molten state.

  This embodiment has multiple advantages, in particular: any assembly for molding hot-melt can be used for carrying out the invention;

  /.....DTD: 4. - any material usually used for spraying self-adhesive adhesive is suitable for spraying hot-melt with minimal modifications, if not any modification; - the hot-melt is completely compatible with the material of the self-adhesive au5 and the block thus formed melts, giving an absolutely homogeneous liquid mass which regains all of its surface adhesive properties on cooling; - the sheathing material is a hot-melt whose nature is not fundamentally different from that of the self-adhesive; these are often joint productions of the same production units, which considerably facilitates the problems of supply and adaptation of specifications; the cooling of the molded mass in its metal mold is relatively rapid, and perhaps if necessary accelerated by cooling of the mold; - on demolding, the mold is released from all the material of the protective layer, and is immediately available for a new molding cycle; the hot-melt which constitutes the epidermis of the block is intimately linked to the material of the block; he remains a member in full and in all circumstances; - the hot melt is fully compatible in the molten state with the self-adhesive; it only represents 0.5 to 3% of the weight of the self-adhesive itself, it does not appreciably modify its permanent tack properties, and does not give rise to any liquid segregation in the melters,

  as products for coextrusion cladding can do.

  The blocks, breads or paving stones resulting from the process according to the invention have all the apparent properties of soaps, and all the operations and manipulations to which the latter lend themselves, coatings

  complementary, stacking, bagging, etc., are directly applicable to them.

  The invention will be better understood by following the nonlimiting examples

described below.

5.

EXAMPLE I

  The specific material is made up of: - an internally siliconized sheet mold, in the shape of a square pyramid trunk, the bottom being constituted by the small base 5 whose side is 10 cm, the walls, 3 cm height, making with the bottom, an open angle of 120;

  - a spray applicator, of the Meltex type (Fraco or Nordson) supplied by a cladding hot-melt consisting of a "hot melt" formulation Based on ethylene-vinyl acetate.

  The hot melt is sprayed for about 5 seconds into the mold, so as to obtain a uniform film which covers the entire

  surface, which consumes about 3 grams of product.

  In the mold thus coated, we now pour 300 g of self-adhesive

  melted, consisting of a formula based on ethylene-vinyl acetate and maintained at a temperature of 140 C.

  The whole is left to spontaneous cooling, and when the surface reaches approximately the temperature of 100 ° C., that is to say according to the ambient conditions, after 30 minutes to 1 hour, the same hot melt is sprayed on the free surface as above, to form the upper envelope (about 0.5 g of hot melt). The mold thus filled is left to spontaneous cooling for sufficient time for

  the mass of the adhesive returns to room temperature.

  We unmold the product which appears as an absolutely non-sticky soap. Such soaps can be stored, for example, by 12, 24 or 48 in ordinary cartons, from which they can be extracted individually after transport and storage, without any

difficulty or inconvenience.

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6. EXAMPLE II (counterexample)

  The pressure-sensitive adhesive of Example I is packaged in commercial silicone trays, organized in 6 rows of 4 cells, with a capacity of 0.6 liters each.

  The self-adhesive is poured at 140 ° C from a tube with 4 orifices allowing 4 cells to be filled simultaneously. Complete filling is carried out by successive displacements of the

  cardboard to present the cells in front of the pouring tubes.

  Temporary storage of 8 to 10 hours allows the final firming of the mass. We close with a lid.

  This carton of 24 cells is packaged and distributed.

  For use, it is necessary to unmold the contents of each cell each operation delivering a loaf of approximately 600 grams, with sticky surface, the handling of which is difficult or unpleasant. EXAMPLE III The material and the operating mode used are those of Example-I, but the hot-melt constituting the cladding veil with the following composition: paraffin 68/70 .............. .............. 33% by weight, Escorez 5320 (Esso) ........................ 33% by weight, Evatane 9003 (Atochem) .......

  .......... 34% by weight, and the self-adhesive itself is a formula for the assembly of feminine hygiene articles, the composition of which is Cariflex TR 1102 (Shell) ... ................ 25% by weight, Escorez 5320 (Esso) ....................... 45 % by weight, .. DTD: Shellflex 451 FC (Shell) ................ 30% by weight.

  Composition maintained at the temperature of 155 C. After pouring the self-adhesive, it is expected that the surface has returned to approximately 120 C, in order to carry out, as in the example, a complementary spraying of the sheathing hot melt on the free surface.

  The blocks obtained by this process are packaged in 12, 24 or 48 units in ordinary packaging; they withstand, without agglomeration the ordinary conditions of transport and storage, including 35 possible exposures at temperatures of 40 C to 45 C for 24 hours or more.

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RESELLERS

  1 - Process for the production by casting of blocks of self-adhesive substance with surfaces devoid of tackiness and of self-agglomeration power under low pressure, comprising the steps of constituting a protective layer affixed to the walls of a mold, cast of the self-adhesive substance melted in the mold thus coated, partial cooling, constitution of a protective layer on the free casting surface, continuation of the partial cooling, constitution of a protective layer on

  the free casting surface, further cooling and demolding of the block, characterized in that the protective layers consist of a non-self-adhesive hot-melt veil.

  2 - Method according to claim 1, characterized in that the veil

  of hot-melt is obtained in place by spraying non-self-adhesive hot-melt in the molten state.

  3 - Process according to claims 1 and 2, characterized in that the non-self-adhesive hot-melt veil consists of substances

  having the character of hot-melt adhesives.

  4 - Method according to claims 1,2 and 3, characterized in that

  the self-adhesive lion hot-melt veil consists of sub20 stanzas or mixtures of substances taken from the group comprising polyethylene, paraffins, polymers and copolymers

  ethylene vinyl acetate, ethylene maleic anhydride, or ethylene acrylic acid.

  - Blocks of hot-melt self-adhesive substance with non-adherent surface 25 characterized in that this surface consists of a

  non-self-adhesive hot melt film.

  6 - Blocks of hot-melt self-adhesive substance according to claim 5, characterized in that they result from a method of casting the self-adhesive substance in the molten state in a mold previously coated by spraying with a non-adhesive hot-melt veil .

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  7 - Blocks of hot-melt self-adhesive substance according to claims 5 or 6, characterized in that the non-adhesive hot-melt adhesive web consists of substances or mixtures of

  substances taken from the group consisting of polyethylene, ethylene-vinylacetate, ethylene-anhydride polymers and copolymers

  maleic, or ethylene acrylic acid.

  8 - Blocks of hot-melt self-adhesive substance according to claims 5, 6 and 7 characterized in that the veil of non-self-adhesive hot-melt substance represents a mass of about 10 of 0.5 to 3% by weight relative to the mass of self-adhesive to be coated.